Physics and Detector Simulations

Norman Graf

June 13, 2000

Common GoalsProvide full simulation of Linear Collider

physics program:Physics simulationsDetector simulationsReconstruction and analysis

Need flexibility for:New detector geometries/technologies Different reconstruction algorithms

Limited resources demand efficient solution, focused effort.

LCD Software Road Map

stdHEP files

fastMC (JAS)

JAS analysis

ASCII raw data

Gismo

Full Recon

Root parser

JAS parser

.lcd filesRoot files

Gismo Material FilesGenerator FilesTrack Momentum Resolution Tables

Parameter Files (JAS)Geometry Description FilesParameter Files (Root)

fastMC (Root)

ASCII recon

Root files

.lcd files

Root Analysis

JAS parser Root parser

Generator(s)

Full SimulationsDetailed descriptions of the detector

elements, complete accounting of physics processes, track swimming, particle showering, etc. Essential for detector development and derivation of fast simulation parameterizations.

GISMO GEANT4

Fast Simulations Simulations based on parameterized,

or simplified detector responsesFast, can be flexible, but limited.

ROOT JAVA

Future Plans

Fully document existing tools.Implement and validate fast simulations:

Full covariance matrix for tracksCalorimeter parameterizations

Improve reconstruction for full simulationtrack finding/fittingcalorimeter clustering

Reconstruction

Default jet findingParticle IDImplement vertex finding/fitting

Develop event data model and implement persistence for reconstructed events.

Undertake physics studies.

ConclusionsBoth full and fast simulation programs exist

S2 and L2 close to production.

Need feedback from detector and physics groupsWhat do you need? When do you need it?

Simulations in a state of flux, input requested.GISMOGEANT4JAS + ROOT fast simulations?

Welcome a wider collaboration on simulation efforts.

Gismo: Full SimulationReasonably full-featured full simulation package - C++

complex geometriesEGS & GHEISHA

cutoffs set at 1 MeVmultiple scattering, dE/dx, etc

Generator input from /HEPEVT/ via FNAL STDHEP I/O packageDigitization

trackinghit points at tracking/VXD layers

calorimeterstotal energy per channel

muon stripsall digi’s have full MC record

Output to ascii file

allows parsers to translate to JAS & Root for further analysis/processing e+e- -~~

Full Sim: Geometry Elements

Most detector types are cylindersinput by ascii detector filetrackers and calorimeters can have

inner/outer skins and endplatestracker/VXD layers can be

individually positioned and sizeduser sets longitudinal cell

composition (multi-materials allowed) and ‘sensitivity’

conical masks configurable

B=3TB=6T

Small Detector

3 Tracker Doublets1.1 mm G10, 600 m Sir = 14, 42, 71 cmouter layers extend to z=149 cm

5 EC Tracker disksz = 31, 61, 91, 121, 149 cminner r follows cos =0.99

Luminosity monitor (Si/W)active from 30-116 mrad

‘Vestigial’ maskcone from r=1.2 cm at z=10 cm to r=20cm at z=155 cm

Coil: 23 cm Al - between EM & HAD cals!

CalorimetryHAD cal: 2 cm Cu; 0.5 cm scintEM cal: 0.2 cm W; 0.03 cm Si

Large Detector144 Layer TPC

r = 25-200 cmlength = 5.8 m4.5 cm Al endplates0.18 cm Al inner/outer skins

Luminosity monitor (Si/W)active from 16-83 mrad

‘Vestigial’ maskcone from r=1.2 cm at z=10 cm to r= 25 cm at z=300 cm

Coil: 40 cm Al - between HAD and MU cals

CalorimetryHAD cal: 0.8 cm Pb; 0.2 cm scintEM cal: 0.4 cm Pb; 0.1 cm scint

Recent Improvements

Detector Descriptions now in XML (J.Bogart)More control over detector configurationEasier to change detector configuration

S1, L1 detectors converted to XML

Refinement of detectors as agreed at SLAC workshop:• Improved end-cap tracking• Finer calorimeter segmentation, theta segmentation

L2 – ready to go (except instrumented masks)S2 – being prepared by Ron Cassell

XML files are available for checking:• http://www.slac.stanford.edu/~jrb/nlc_detectors/

Many Bug fixes

Moving from ASCII to SIO File format

Beam Background Overlays (Gary Bower)

Take output from Guinea Pig beam simulation (from IR/backgrounds group)

Feed into full Gismo simulationBuild library of simulated background

bunchesOverlay backgrounds on signal events at

start of reconstructionAdjust timing of hits (for TPC e.g.)Add energy in calorimeter cells

Allows to change #bunches/train, bunch timing

JAS Physics UtilitiesPhysics Utilities

4-vector, 3-vector classesEvent shape/Thrust finderJet Finders

Many kT algorithms implemented (e.g. Jade and Durham )Extensible to allow implementation of other algorithms

Contributed AreaAnalysis Utilities and sample analyses provided by

users

2 Event Displays2D - Suitable for debugging reconstruction and

analysisWired for full 3D support

Particle Hierarchy Display

2D Event Display

Wired (M. Donszelmann – CERN)

Physics GeneratorsThere have been recent updates to

Pandora.A general purpose framework which allows

polarization and initial-state interactions to be simulated.

The Pandora-Pythia interface exists.Any generator producing STDHEP-format

output can be used as input to simulationsPYTHIA, ISAJET, etc.

Tracking ReconstructionHit Smearing/Efficiency (since Gismo gives “perfect”

hits)Random Background overlayTrack Finding:

uses M.Ronan’s (TPC) pattern finding Tuned for Large + Small detector

Track Fitters:SLD Weight Matrix FitterCan do Single Detector or Combined fit (e.g. VTX+TPC)

What’s still needed:More Track Finding Algorithms (Cheater, Projective Geometry)End Cap tracking, Hit MergingKalman Filter (incorporating multiple scattering)

Calorimeter ReconstructionCluster Finding

Three Clustering Algorithms Currently ImplementedCluster Cheater (uses MC truth to “cheat”)Simple Cluster Builder (Touching Cells)Radial Cluster Builder

• All algorithms tend to produce many very low energy clusters - important to set sensible thresholds

Still Needed - Cluster Refinement StageCombine HAD + EM clustersEndcap + Barrel overlap region

In Progress - Track Cluster AssociationInitial Implementation Done by Mike RonanOutput Format defined by Gary BowerNeed to Extend Definition of Clusters

Directionality, Entry point to calorimeter